Construction progress monitoring is software that compares scans of a building site with the site's 3D model, to show how much has really been built and to find mistakes early. The scans are taken by drones, by 360-degree cameras carried on a helmet, or by walking robots. The 3D model is the BIM model that the designers drew.
On most sites, progress is still checked by people. An engineer walks each floor with the drawings and writes down what is done. This takes days on a large site, and different people judge "done" differently. Owners and lenders often release money according to progress, so these numbers matter.
The software works in three steps. First, the site is captured. A 360-degree camera takes photos every few seconds as a person walks the floor, or a drone flies over the site, or a laser scanner on a robot measures millions of points. Second, the software turns the capture into a 3D picture of the site and lines it up with the model. Third, it uses computer vision to recognise each element, such as a column, a duct or a wall, and compares it with the same element in the model.
Consider a 14-storey commercial building under construction in Kochi. Every Monday, a site engineer walks each floor with a 360-degree camera fixed to his helmet. On the eighth floor, the software reports that 62% of the air-conditioning ducts and 40% of the sprinkler pipes are installed. It also finds that one partition wall has been built 30 cm away from where the model shows it. The wall is still bare blockwork, so moving it now costs a day's work. Found after the plaster, the tiles and the wiring, the same fix would cost far more. The photos of every corner are saved with their date. So a later dispute about what was built, and when, can be settled from the record.
The progress figures go into construction management software, where they update the schedule. They also go to construction risk prediction, which uses them to warn about delays. Aerial images of the whole site, used to measure earthwork and stockpiles of sand and aggregate, come from drone surveying.
A model that is kept up to date with scans in this way becomes a record of what was actually built. After handover, it can become the starting point of the building's digital twin, a digital copy of the real building that is kept up to date with data from it.